1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to methods and devices for accessing the pericardial space in a minimally invasive manner.
The human heart is enveloped within a tissue structure referred to as the pericardium. The pericardium includes two major portions. The portion of the pericardium which lies immediately over the surface of the heart is referred to as the visceral pericardium. The second portion is formed as a sac around the visceral pericardium and is referred to as the parietal pericardium. Normally, the visceral and parietal pericardia lie in close contact with each other and are separated only by a thin layer pericardial fluid. The space (really more of a potential space) between the visceral and parietal pericardia is referred to as the pericardial space.
Access to the pericardial space can be necessary or beneficial under a variety of circumstances. Open surgical access can be obtained via open sternotomy where the patient""s sternum is divided and the parietal pericardium exposed. Alternatively, the pericardial space can be approached from a skin incision made below the xiphoid through which the parietal pericardium is identified. Such approaches, however, are highly traumatic, requiring general anesthesia and useful only under compelling circumstances. Access to the pericardial space can also be achieved using a thoracoscopic approach. Under general anesthesia, the left lung is deflated after which multiple holes are made for the thoracoscope and various instruments. The pericardium is then entered using standard videoscopic techniques. The thoracoscopic approach typically requires the placement of a chest tube and admission to the hospital for the initial 1-2 post-operative days.
In patients who require drainage of a large pericardial effusion, a simple percutaneous approach can be used. Through a small (2-4 mm) cutaneous incision between the xiphoid and costal cartilage, a spinal needle (18-20 gauge) is advanced in a superior/posterior fashion. At appropriate intervals, the stylet is removed and fluid aspiration is attempted. If no fluid is obtained, the stylet is replaced and the needle advanced again. This cycle is repeated until fluid is aspirated. If the needle is advanced too far, the heart can be punctured and is why a large pericardial effusion must be present on ensure adequate separation of the visceral and parietal pericardia.
A minimally invasive method for accessing the pericardial space is described in U.S. Pat. No. 5,827,216 to Igo et al. A pericardiocentesis apparatus is introduced via a subxiphoid approach to the heart. A vacuum is applied at a distal end of the device to form a xe2x80x9cbleb,xe2x80x9d i.e., a locally expanded region in the pericardium. A needle can then be penetrated through the bleb, and the needle used for drawing fluids, delivering drugs, or the like. Although theoretically plausible, the ability to reliably maintain a seal against the pericardium can be problematic.
For these reasons, it would be desirable to provide additional and improved methods and apparatus for the minimally invasive access to a patient""s pericardial space. The methods and devices should be suitable for a wide variety of minimally invasive approaches to the pericardium, including at least intercostal/transthoracic and subxiphoid approaches, and the like. The methods and devices should further provide for secure and stable capture of the parietal pericardium and permit the opening of a large space or volume between the parietal and visceral pericardia. Such access methods and apparatus should be useful for a wide variety of procedures to be performed in the pericardial space, including fluid withdrawal, drug delivery, diagnostic and therapeutic electrophysiology procedures, pacemaker lead implantation, defibrillator lead placement, transmysocardial revascularization, transmysocardial revascularization with drug delivery, placement of the left ventricular assist devices, placement of the arterial bypass graphs, in situ bypass, i.e., coronary artery-venous fistulae, placement of drug delivery depots, closure of the left arterial appendage, and the like. At least some of these objectives will be met by the invention described herein.
2. Description of the Background Art
U.S. Pat. No. 5,827,216, describes a pericardial access tube which draws a vacuum on the parietal pericardium as part of an access procedure, as discussed above. U.S. Pat. No. 5,071,428, describes a method for accessing the pericardial space for defibrillation lead implantation by grasping the parietal pericardium with forceps and cutting the pericardium with a scalpel. U.S. Pat. No. 4,281,659, describes a probe system having paired helical wires for securing the probe to a patient""s skin. U.S. Pat. No. 4,164,943, describes a catheter anchor having multiple helical wires for securing the anchor to a patient""s skin. U.S. Pat. No. 5,226,890, describes a trocar cannula anchor having a tapered thread for placement in a percutaneous tissue penetration. U.S. Pat. No. 5,332,398, describes and intramedullary catheter having a threaded end for implantation into a bone.
The present invention provides methods, apparatus, and kits for accessing an anatomic space having a wall with an outer surface. The wall may consist of a membrane, a capsule or the adventia, muscularis and endothelial layers of a hollow organ or vessel. The methods, apparatus, and kits are particularly useful for minimally invasive access procedures, but could also be used for accessing internal anatomic spaces where initial access to the wall of the outer surfaces achieved via open surgical or other techniques. The present invention will be particularly useful for accessing a patient""s pericardial space for performing a wide variety of procedures, generally as set forth above.
The phrase xe2x80x9canatomic spacexe2x80x9d is meant to include any natural, potential, or created space or cavity within a patient""s body where it may be desirable to gain access for surgical, diagnostic, therapeutic, or any other purpose. Usually, the anatomic space will be within an organ or structure located beneath the patient""s skin, such as the pericardial space which lies between the visceral and parietal pericardia, both of which lie beneath the chest wall and rib cage. Other internal organs which may be accessed include the intestines, fallopian tubes, gall bladder, kidneys, and the like.
Methods according to the present invention for accessing an anatomic space having a wall with an outer surface comprise embedding a distal end of an access tube into the outer surface. An access device, such as a stylet, needle, or other piercing instrument, may then be introduced through the access tube, penetrating the wall, and into the anatomic space while the access tube stabilizes the wall. Embedding the distal end of the access tube can be achieved in a wide variety of ways. Typically, an anchor structure at the distal end is engaged against the outer surface of the anatomic space wall and subsequently penetrated into the surface. For example, the anchor structure may comprise one or more penetrating points which are embedded into the wall by rotation of the access tube, distal advancement of the access tube, or the like. While the penetrating points will typically be fixed on the access tube, it will also be possible to provide springloaded or other selectively deployable penetrating points which can be embedded into the anatomic space wall while the access tube is held stationary. After the distal end of the access tube has been embedded into the anatomic space wall, the wall will usually be drawn or otherwise manipulated increasing the available access volume therein. In particular, by increasing the available volume, the risk of accidental injury from advancement of the access device into deep structures is significantly reduced. Increasing the access volume, however, can have other benefits. For example, it can improve the ability to image the anatomic space using a fiberoptic imaging scope, permit the introduction of various devices, drug delivery structures, or the like.
In preferred aspects of the present invention, the access device will be a hollow needle or stylet, and a guidewire will be positioned through the needle and into the anatomic space. The needle can then be withdrawn, and the guidewire used for access of a variety of diagnostic, therapeutic, or other catheters and devices.
In a further aspect of the method of the present invention, a pericardial space between the visceral and parietal pericardiums is accessed by percutaneously positioning a distal end of an access tube over the parietal pericardium. Positioning can be achieved either by a transthoracic or a subxiphoid approach beneath the sternum or from the abdominal cavity through the diaphragm, or the like. Once in position, a distal end of the access tube is embedded into the parietal pericardium in a manner which does not engage the visceral pericardium. The access tube is then drawn or otherwise manipulated to separate the parietal pericardium from the visceral pericardium to enlarge the available volume of the pericardial space therebetween. An access device, again usually a needle or hollow stylet, is then advanced through the access tube penetrating the parietal pericardium entering the pericardial space. Guidewires may then be positioned and a variety of particular protocols performed, generally as listed above.
The present invention still further provides systems comprising an access tube and a needle, stylet, or other equivalent device. The access tube has a distal end which can be selectively embedded into tissue, and the needle, stylet, or other access device has a lumen which is useful for subsequent placement of a guidewire, as generally described above. Optionally, the system may further comprise the guidewire capable of being positioned in the anatomic space through the needle.
The present invention still further provides kits for accessing the pericardial space of a patient. The kits comprise an access tube having a distal end which can be selectively embedded into tissue. Exemplary access tubes are described above. Kits will further comprise instructions for use according to any of the methods set forth above. Kits may optionally further comprise a package for holding at least the access tube and usually the instructions for use. Exemplary packages include boxes, trays, pouches, tubes, and the like. Usually, at least the access tube will be maintained sterilely within the package. Optionally, the needle, stylet, or other access device, may be included. Further optionally, the guidewires used for the methods of the present invention may also be included within the kit.